For completeness, I have double-click opens groups in a new window unchecked, although checked would be fine, too. Also, double-click opens documents externally is unchecked.
When I double-click on a tag, the pane that lists all the files focuses on that tag. The pane or area I’m talking about is between the sidebar and the document area with View->Preview set to Widescreen.
Once focused on a tag, click the Tags icon on the bottom edge of the sidebar or click Tools->Filter->Tags.
This will give you a list of all the tags applied to documents tagged with the tag you’re focused on. You can click tags in that map to further refine the tag filtering.
You can also navigate around in the sidebar, preserving the tag filter.
Does this do what you need?